PITTSBURGH -- On Saturday, the Pirates and the Nationals will meet at PNC Park for something routine: A weekend baseball game.

But this one will be marked with a certain weight of grief and remembrance, as the two markets will observe 20 years since the horrific attacks of Sept. 11, 2011.

Both teams’ regions were directly impacted by the terrorist attack. Shortly after the Twin Towers were struck in New York City, Flight 77 was hijacked and crashed into the Pentagon in Washington, D.C., killing 189 staffers and passengers.

Flight 93, which was taken over by a fourth set of hijackers and headed for either the White House or the U.S. Capitol, was diverted by a brave group of passengers who tried to overtake the terrorists and, in the process, forced them to land near Stonycreek Township, about an hour and a half southeast of PNC Park by car. The crash killed all 44 people on board.

Before Saturday’s game, the Pirates will host the families of some of the victims who died in the Flight 93 crash. Colonel Chris Whalen, whose cousin Richard Guadagno was killed in the tragedy, will throw out the first pitch, and during a moment of silence, the Pirates will display the names of all of the victims on the videoboard.

More than 200 members of Pittsburgh’s police, firefighters and EMS crews will unfurl a large United States flag as Allegheny County sheriff Richard Manning sings the National Anthem. Then, the 316th ESC Army Reserve command based in Corapolis, Pa., will be honored before Manning sings “God Bless America” in the seventh-inning stretch.

“I think every year, this day has a special meaning,” Pirates manager Derek Shelton said. “And when you’re playing a team that is in the nation’s capital in a place that was greatly affected -- I mean, the whole country was affected -- but affected directly, I think it does take a different meaning.”

With the Nationals on the road this year on Sept. 11, the team held a Heroes Day recognition on Monday afternoon at Nationals Park before traveling to Atlanta and Pittsburgh. The organization honored more than 20 current Pentagon employees who were present there on Sept. 11. Pregame ceremonies also included the nation’s colors being presented by the Central Intelligence Agency Honor Guard, a moment of silence and a video from the Department of Defense.

For Nationals manager Dave Martinez, a New York native, Sept. 11 is “a day that, personally, I will never forget.” Martinez was playing first base for the Braves the night Mets Hall of Famer Mike Piazza hit a go-ahead home run on Sept. 21, 2001, the home game after the attacks.

“It was a horrific feeling that day,” said Martinez, who plans to talk to his team about Sept. 11 and its significance in baseball on Saturday. “For what seemed like a short moment, we were able to give some of the people and fans a chance to just try to forget and go out there and just play baseball and have fun. I’m very elated that I was part of that.”